Such bipolar plates are generally used in fuel cell stacks. These are a plurality of fuel cells that are connected electrically in sequence and follow one another successively in a stack direction. The individual fuel cells are separated from each other by bipolar plates. A bipolar plate must be electrically conductive at least in areas over its entire extension in the direction of thickness and, since it is generally in contact with acidiferous electrolytes during operation, must also be acid-resistant.
Conventional bipolar plates have therefore been manufactured from sintered graphite, since graphite is both electrically conductive and acid-resistant. Bipolar plates made of sintered graphite are expensive to manufacture and difficult to handle, however, since sintered graphite is a very brittle material.
One advantageous alternative to this that is cost-effective and easy to handle is the bipolar plates defined at the outset. With a properly selected thermoplastic binder, they can have a high level of chemical resistance to acids. Due to the carbon fibers, they are highly electrically conductive. One such bipolar plate is known, for example, from printed publication DE 102 19 384 A1. In this bipolar plate, carbon fibers with a length of less than one millimeter are bonded in a thermoplastic plastic matrix. The carbon fibers are uniformly distributed in the plastic matrix, which leads to a given electrical conductivity.
However, due to the arrangement of the bipolar plate between two electrodes of different polarity, one of which belongs to another of two fuel cells arranged immediately adjacently in the stacking direction, it can be advantageous if the electrical characteristics of a bipolar plate can be set in a defined manner, for instance in order to enable the bipolar plates to be adapted to characteristics of the electrodes adjacent to them.